Alzheimer's disease (AD) refers to a nervous system degenerative disease that severely affects the quality of life of the elderly. AD is the main type of senile dementia and the main cause of cognitive deterioration. According to multiple results of epidemiological surveys in China, the prevalence rate of AD in people over age 65 is about 5%, and its incidence increases with age generally. At present, there is no any drug that can be used to reverse cognitive impairment effectively. Acetylcholinesterase inhibitors (donepezil, rivastigmine, huperzine A, galanthamine) have some therapeutic effect on the patients with mild to moderate AD, but they may only temporarily alleviate symptoms and are not able to prevent further neuronal attenuation and also have some severe side effects. The combined application of cerebral blood flow and cerebral metabolism modifiers, such as oxiracetam, have shown to be effective in improving memory, but more often they are used as an intelligent improving reagent. The development of drugs related to amyloid precursor protein and amyloid β-protein seemed to be a promising approach until the release of clinical trial results for a series of secretase inhibitors provided by some major pharmaceutical companies such as Eli Lilly, and thus such approach may not be continued.
As AD may have different causes, the drug administration of single route or with single target may not be desirable; for the treatment of such disease, “one drug one target” is not an effective approach. A multifunctional drug refers to a drug having multiple treatment mechanisms for the same disease. Such multifunctional drugs are considered to have more potential than commonly used “one drug one target” drugs. Multifunctional drugs may be used for treating diseases such as cognitive and movement disorders, depression, schizophrenia, and other complicated diseases (Morphy et al. Drug Discov Today. 2004, 9(15): 641-651).
In the past, we made certain structural modifications over compound J147 synthesized by Professor Schubert of the Salk Institute, and also introduced a Ligustrazine moiety from traditional Chinese medicines to obtain compound T-006 with multifunctional therapeutic mechanisms. T-006 is a trifluoroacetyl hydrazide compound as used for the treatment of AD may have multiple mechanisms, including inhibiting glutamate receptor, activating MEF2 transcriptional activity, improving cognitive ability, neural differentiating, free radical scavenging, and protecting cells such as especially nerve cells.
Glutamate receptors may be divided into two types: the first type is ionic receptor, including N-methyl-D-aspartate receptor (NMDAR), kinase receptor (KAR) and α-amino-3-hydroxy-5-methyl-4-isoxazole receptor (AMPAR), which are coupled with ion channels to form receptor-channel compounds to mediate fast signal transduction; and the other type is of metabotropic receptors (mGluRs), which are coupled to G-proteins within the membrane. These receptors are activated to produce a slower physiological response through a signal transduction system consisting of G-protein effectors, second messengers, etc. (Wang S J, Yang T T, et al. Drug News Perspect, 2005, 18 (9): 561-566). Glutamate is the most abundant and important amino acid in the central nervous system for participating synaptic transmission and maintaining normal physiological functions of nerve cells. Under normal circumstances, the release, intake and re-absorption of glutamates remain in a dynamic equilibrium. However, if over release occurs or uptake is interrupted, glutamate may be accumulated in the brain which may cause a sharp increase in its concentration, while over activation of the receptor may cause a wide range of pathological damage on brain tissues (Kumar A, Zou L, Yuan X, et al. Journal of neuroscience research, 2002, 67(6): 781-786). Such excitotoxic effect of glutamate is closely related to the occurrence and development of various neurodegenerative diseases, and is shown as one of the important mechanisms leading to neuronal death in neurodegenerative diseases.
MEF2 includes four different isoforms (MEF2A-D) and is one of the first nuclear transcription factors found in muscle. It binds to the sequence of A/T enriched in DNA and regulates the expression of many genes involved in the formation and development of muscle. Many studies confirmed that MEF2 is not only highly expressed in muscle tissue, but also be abundant in the nervous system, and plays a regulating role in cell differentiation, growth, morphology, survival and apoptosis (Potthoff M J, Olson E N, et al. 134 (23): 4131-4140, McKinsey T A, Zhang C L, Olson E N, et al. Trends Biochem Sci, 2002, 27: 40-47). Many experiments show that MEF2 can regulate the growth of dependent synapsis and the formation of long-term memory, but the role of MEF2 in promoting memory formation is different from that of the traditional transcription factor CREB (Josselyn S A, Nguyen P V, et al. Curr Drug Targets CNS Neurol Disord, 2005, 4 (5): 481-497). The activation or inhibition of MEF2 is mainly determined by its DNA-binding affinity: PKA, CKII and GSK3β, p38, ERK5 and CaMKIV, PP2B may activate tanscriptional activity of MEF2 through acetylation or ubiquitination of the C-terminal residues of MEF-2; whereas inhibition of tanscriptional activity of MEF2 may be through binding to HSc70 of MEF2D through lysosomal degradation of neurotoxic substances and the expression of caspase; HDAC can inhibit the transcriptional activity of MEF2 through activation or inhibition by PP1α and CaMKIIα respectively (Rashid A J, Cole C J, et al. Genes, Brain and Behavior, 2014, 13 (1): 118-125). The expression of MEF2 can improve the survival rate of newborn neurons, while the mutation of MEF2C can lead to the increase of the number of apoptotic neurons and the loss of memory, which may cause a series of neurological diseases Wang et al. demonstrated that microtubule-associated protein Tau, involved in the pathogenesis of AD, is one of the substrates of glycogen kinase 3 (GSK3), and GSK3 inhibits the activity of MEF2D by direct phosphorylation, which process is involved in the degenerative changes of AD (Wang X, She H, et al. Journal of Biological Chemistry, 2009, 284(47): 32619-32626). The latest study by Professor Lipton indicates that the pathogenesis of PD is also associated with the inhibition of transcription between MEF2C-PGC1, which caused mitochondrial dysfunction, apoptosis and cell death (Ryan S D, Lipton S A, et al. Cell, 2013, 155 (6): 1351-1364).
One of the major pathological features of AD patients is amyloid beta deposition, commonly known as senile plaques. An important change of their behavior is learning and memory dysfunction. β-amyloid protein, abbreviated as Aβ, is produced by a series of secretase hydrolysis of its precursor protein APP. There are two main forms of Aβ; Aβ40 and Aβ42, wherein Aβ42 is of about 10%. Because of its high hydrophobicity, Aβ42 is easy to form fiber which is the major component of brain plaques (commonly known as senile plaques) found in the brains of patients with AD. Studies have indicated that a single Aβ does not produce toxic effects on the body, but the formation, aggregation and deposition of a large number of Aβ can cause a series of neurotoxicity, such as, interfering with synaptic activity, leading to protein dysfunction; inducing calcium influx leading to promote the phosphorylation of Tau protein, and the like (LaFerla F M, et al. Nature Reviews Neuroscience, 2007, 8(7): 499-509).
Oxidative stress refers to the physiological process of oxygen and antioxidant system imbalance caused by the body produces a large number of oxide intermediates when the body is sitmulated. The imbalance tends to the generation of large amounts of free radicals and the activity of the antioxidant system is reduced, leading to oxidative damage to the body. These free radicals include reactive oxygen species (ROS) and reactive nitrogen species (RNS). The generation of free radicals is very complex and closely related to various physiological and biochemical processes (Conrad et al. Neurochem Int. 2013, 62(5):738-49). Because of the large number of polyunsaturated fatty acids in the phospholipid bilayers of neurons, which prone to lipid peroxidation, neuronal cells are more sensitive to oxidative stress than other cells (Facecchia K, et al. Journal of toxicology, 2011, 2011.). Oxygen metabolism damage in the central nervous system can produce more severe oxidative stress, leading to further damage to the nervous system (Mohsenzadegan et al. Iran J Allergy Asthma Immunol. 2012 September; 11 (3): 203-16). In the normal physiological condition, excessive free radicals and hydrogen peroxide (H2O2), singlet oxygen, ozone (O3) and other reactive oxygen species can be quickly cleared by the antioxidant system, but under the pathological conditions, this ability to remove is damaged. The accumulation of reactive oxygen species can cause nucleic acid fragmentation, enzyme passivation, polysaccharide depolymerization, and lipid peroxidation, eventually leading to neuronal death (Yan et al. Free Radic Biol Med. 2013; 62: 90-101). There are many factors that cause oxidative stress, and Aβ, metal ions, and mitochondria are all considered to play an important role in the process of oxidative stress. The content of soluble Aβ has a good linear relationship with the production rate of hydrogen peroxide. Aβ can change the permeability of calcium channels, activate NADPH oxidase II (NOX2), transfer electrons from NADPH to oxygen, increase the rate of ROS production, while Aβ has a strong affinity for metal ions with redox activity (Pimentel et al. Oxid Med Cell Longev. 2012; 2012:132-146). Aβ can produce hydrogen peroxide after binding to these active metal ions. Studies have shown that pro-oxidants can promote the production of Aβ, however antioxidants, such as vitamin E and other free radical scavengers can prevent Aβ damage to neurons and improve cognitive impairment.
Mitochondria are the main sites and the main donor of energy in the intracellular redox reaction, which produces more than 90% of the total free radicals in the cell. Thus, the normal function of the mitochondria has significance meaning for maintaining the normal physiological activity of the neurons (Yan et al. Free Radic Biol Med. 2013, 62:90-101). It has been suggested that various neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and progressive supranuclear palsy (PSP) and so on, mainly due to functional abnormality of neuronal mitochondria (Du et al. Int J Biochem Cell Biol. 2010, 42(5): 560-572). Quantitative morphological counts of different types of mitochondria (normal, partial damage, and complete damage) in the brain neurons of AD patients showed that the normal mitochondrial content of the AD neurons was significantly reduced and the content of completely damaged mitochondria was significantly increased, compared with the neurons in normal brain of the same age (Beal et al. Curr Opin Neurobiol. 1996 6(5): 661-6666). Mitochondrial damage leading to neuronal oxidative damage plays a major role in two aspects: one is to make the electron transport chain (ETC) dysfunction, so that free radical content increased, and the other is to reduce activity of mitochondrial antioxidant system by reducing content of mitochondrial glutathione, coenzyme Q, vitamin C, vitamin E and other antioxidant small molecules and some oxidation reaction catalytic enzymes.
The Salk Institute has completed major preclinical studies of pharmacology and toxicology of J147, and the preliminary test results if which fully demonstrated that trifluoroacetyl hydrazide compounds have good pharmacological properties, and the results of clinical trials are now submitting to the FDA. In the present invention, tetramethyl pyrazine (TMP), the main active ingredient in the traditional Chinese medicine chuanxiong, is introduced into J147 to obtain a new compound T-006, thus giving T-006 a multiple mechanism of both J147 and TMP for multifunctional treatment of AD activity.